Spectral Characteristics and Mapping of Lithium-rich Playas for Use in Western U.S. Basin and Range Mineral Assessment of Lithium

Scientific Issue and Relevance

The USGS identified the need for more assessment and exploration of lithium-bearing mineral deposits. The major source of current lithium production is from brines extracted from playas located in places such as Clayton Valley, Nevada, Salar del Atacama, Chile, and Salar del Hombre Muerto, Argentina. Lithium-rich playa exploration in the U.S. is focused on the U.S. Basin and Range province where the Clayton Valley playa and at least 80 additional playas of similar or greater size are located.

According to the current deposit model, lithium-bearing playas are situated in closed basins that are surrounded by ash-tuff flows that have been partially hydrothermally altered to produce lithium-rich clays such as hectorite. In addition, the deposit model indicates that the significant playa deposits of lithium-bearing brines also exhibit current geothermal activity and the presence of gypsum and halite, although these associations are not fully understood. The lack of a detailed mineralogical assemblage for these types of deposits is a significant shortcoming, especially with respect to developing remote sensing assessment techniques. An increased understanding of the spectral characteristics and surficial mineralogy of lithium-rich playas will improve ASTER mineral mapping algorithms for use in creating regional mineral maps.

Methodology to Address the Issue

To better understand the mineralogy of these deposits we plan to compile and examine mineral maps of the known lithium-bearing playas in the U.S., Chile, and Argentina using field and remote sensing data. We also plan to utilize an existing geochemical model that predicts which playa mineral assemblage should develop from specific types of rocks and deposits (Eugster, 1980) that are associated with mapped lithium-rich brines. New spectral characteristics and pathways of lithium-rich clays, which are being examined in other USGS projects will also be utilized in ASTER mineral mapping of playas. This approach will help us identify the mineralogical assemblages associated directly with these deposits and possibly with mineral assemblages that surround the playas. Such an approach will provide larger targets and vectors toward Li-bearing brines. 

Project Goals

1. Determine mineralogy associated with lithium rich-playas using Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER), and Airborne Visible / Infrared Imaging Spectrometer (AVIRIS) data, and field work.
2. Develop and validate mineral mapping algorithms using ASTER data.
3. Produce regional mineral map of U.S. Basin and Range using ASTER data and mapping algorithms.
4. Develop basic ranking system for each playa based on mapped mineral assemblages.
5. Produce map of ranked playas of U.S. Basin and Range for U.S. lithium assessment.

Project Tasks

• Key minerals that are associated with lithium-rich playas at Clayton Valley, Nevada, Salar de Atacama, Chile, and Salar de Arizar, Argentina will be identified and mapped using ASTER data and on-site work
• Acquire and calibrate additional ASTER data for regional mapping of the study area
• Investigation of types of lithium-rich deposits
• Spectrally map part of the Clayton Valley deposit

References

Eugster, H.P., 1980, Geochemistry of evaporitic lacustrine deposits: Annual Review of Earth and Planetary Sciences, v. 8, p. 35-63, https://doi.org/10.1146/annurev.ea.08.050180.000343.

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